I want info on Nautilus Circuit Training

Joined the Y. They have a Nautilus circuit that I try to use every other day. It's kinda fun, but I don't know what I'm doing really. I don't have lofty fitness goals, but I want to be in better shape in general. My girlfriend made a chart to track weights and reps for each machine so I guess that's a good step, but I don't know if what I'm doing is good or a waste of time.

Can anyone give me some tips?

Currently I get to the Y, do 1/4 mile around the track just to get my heart rate up and get things moving, then hit the circuit. They have 18 machines of all different types. I do every one of them at the max weight I can safely handle with enough reps until I can't go further. Then I move to the next machine until I'm done. Then I go stretch. Process takes just over an hour. Good? Bad? Stupid? Dangerous? I have no clue. Fill me in plx.